We are concerned with mechanisms by which a cell regulates the expression of its genetic repertoire so as to coordinate complex cellular activities during both normal growth and nutritional deficiency. Although all cells are capable of this widespread integrative control, we have utilized the bacterium E. coli because molecular genetic approaches are simplified. Previous project work has described the discovery, characterization and regulatory attributes of a regulatory nucleotide, ppGp, that is thought to participate in the regulation of at least half of the genes of E. coli. Amber mutants have been isolated that are defective in ppGp regulation and map in chromosomal regions encoding ribosomal proteins. These probably represent defects in the ribosomal site for ppGp synthesis. In addition a mutant has been isolated that is completely defective in ppGp synthesis, the first such example in prokaryotes. Attempts to reproduce ppGp inhibition of ribosomal RNA promoters using highly purified biochemical systems available through genetic cloning have revealed that unforeseen components or structures are prerequisites for regulation. These are being explored.